Did I write 1/4 inch per foot???!!!
I meant 1/8 per foot, my brain typed the usual code number for drains. Stupid brain!!
If you were to do 1/4 inch per foot on a 30 foot gutter...Hmmmm.Stupid brain!!!

That would be 7 1/2 inches probably on a 1x8 facia board!!!
Way to much.

Stupid brian... oh I ment brain!!!!
On my way to 100 POSTS!!!!!
InspectorD

This aint the the most accurat but I just eye ball it from the ground with someone on the roof or ladder, On big jobs we just stick to the siding or roof and contract the gutters out.
These guys,thats all they do and are faster than I would be.
One old timer once told me though, he would keep a marble in his bag and pitch the gutter on how it roll when layed inside.